Patent GB-272612-A (GB)
Title: Intercommunication system for printing telegraph stations
IPC: H04L12/04
Filed: 1926-03-17
Abstract: 272,612. Standard Telephones & Cables, Ltd., (Western Electric Co., Inc.). March 17, 1926. Type-printing telegraphs.-At each of a number of stations with printing-telegraph transmitting and receiving equipment a switching device is' provided for establishing selectively a printing-telegraph crcuit with certain of the other stations. The figure shows the connections of two central stations A and B, and two substations a and b such that either central station may signal the other central station and each substation may signal either central station to establish printing telegraph communication. Each central station is provided with a key 2 or 4 for communication with the other central station and with keys 7, 8 or 15, 14 each for communication with a particular sub-station. Communication between central stations. The operator at station A desiring to use the printer set 25 to transmit a message to be printed at station B moves his key 2 downwards to close a circuit from ground through winding of relay 29, lower left make-before-break contacts of key 2, lead 51, upper left and lower left normally closed contacts of key 4 at station B, lamp 5, and battery to ground. The operator at station B seeing the lamp 5 lit, and desiring to receive the message on the printer-set 32, moves his key 4 upwards. This opens the circuit of lamp 5 and the circuits of normally-energized relays 29 and 10 at stations A and B respectively. The armatures of these relays thereupon close the power circuits for the motors 28, 36 driving the corresponding printers. The printing communication circuit is from battery through relay 31, transmitter TR of set 25, lower right makebefore-break contacts of key 2, lead 51<1>, upper right make-before-break contacts of key 4, printer-operating magnet 34, make-before-break contacts of keys 14 and 15, and upper left make contact of key 4 to ground. The transmitter TR operates to produce breaks in this circuit corresponding to the signals, and the printer-operating magnets 31, 34 respond accordingly. On completion of the message the keys 2 and 4 are restored thus energizing the relays 29, 10 to stop the motors 28, 36. Communication between a sub-station and a central station. The operator at sub-station a desiring to print a message at station A operates a key 47. This opens the circuit of a relay 46 at station A. to light a lamp 57. The operator at station A seeing this lamp lit, and desiring to use the printer-set 25, moves his key 8 downwards, thus breaking a circuit through relays 48, 49, 45, 55, and 56. De-energizing of relay 45 opens the circuit of the lamp 51 and closes that of a lamp 59 which indicates that the stations a and A are in communication. Deenergizing of relay 55 similarly lights a lamp 58 at station B. De-energizing of relay 48 closes the power circuit for the motor 62 at sub-station a, and, simultaneously, the de-energizing of relay 29 by opening of the right-hand contacts of key 8 closes the power circuit of the motor 28 at station A. The printing communication circuit is from battery through winding of relay 31, transmitter TR of set 25, lower right normally-closed contacts of key 2, lower right make-before-break and upper right normallyclosed contacts of key 8, and back contact of relay 49 to transmitter TR and printer-operating magnet 43 at station a. If the operator at station a desires to print a message at station B, he operates a key 64 to short-circuit a resistance. 53. The resulting increase of current through relay 56 is sufficient to overcome the biasing current, thus moving the armature to close the circuit of a lamp 65. The operator at station B seeing this lamp lit, and desiring to use the printer-set 32, moves his key 14 upwards to close the corresponding printing communication circuit.